Recently, brain-computer interface (BCI) technology, particularly with regards to neuroprosthetics, has become a common area of interest in the neuro-engineering realm. Accelerated interdisciplinary research has been achieved by the collaboration between neuroscience, medicine, and rehabilitation engineering, bringing the common goal of technology for treating severe motor impairment closer to reality. This endeavor has also shown potential in the elucidation of the neural mechanisms inherent in the central nervous system. Devices for brain signal acquisition, essential components of BCI systems, have lead to a plethora of novel bio-signal acquisition modalities. For example, clinical cortical monitoring devices are routinely utilized for monitoring and mapping epilepsy activity. Recording and interpreting electrical signals from the cortex has been used for BCIs, which can enhance communication for individuals with conditions such as spinal cord injury or amyotrophic lateral sclerosis (ALS). In addition, therapeutic stimulation has been used for stroke rehabilitation, alleviation of chronic pain, and seizure control.
The Electroencephalogram (EEG) has been the primary focus of clinical BCI technology thus far, due to its safety and convenience. However, EEG signals lack the resolution, amplitude, and bandwidth offered by more invasive methods. Various invasive microelectrode arrays such as Michigan probes and the Utah electrode arrays have been developed within the last 20 years to achieve more localized neural signals. Since these devices are based on silicon microfabrication technology, with micron scale features, they are capable of detecting single neuron activity. Though their capability to detect minute changes in action potentials is very impressive, inserting the probes arrays into brain tissue can cause significant scar tissue accumulation around the device (cell encapsulation/ensheathing), which may decrease the intensity of signal and the signal to noise ratio (SNR), and can lead to a loss of recording ability.
Recent Electrocorticogram (ECoG) studies have shown promise for its use as an alternative method for BCI control. Unlike invasive electrodes requiring penetration into the cortex, ECoG electrodes are placed on the cortex surface, which can reduce risk of possible implant related damage. ECoG also has some advantages over EEG including higher spatial resolution, broader bandwidth and higher amplitude than EEG. Recent studies have shown that ECoG signals can be used for BCI control with minimum training and they contain detailed aspects of motor actions, which was previously thought to be only possible using invasive electrodes. However, these devices are much larger than necessary and made with sub-optimal materials. In addition, there are issues of compatibility of the device in physiological environments.
Therefore, it is a primary object and feature of the present invention to provide a thin-film microelectrode array that is tailored specifically for long-term, minimally invasive cortical recording or stimulation.
It is a further object and feature of the present invention to provide a thin-film microelectrode array that has an improved signal-to-noise ratio and higher spatial resolution over the current electrode modalities.
It is a still further object and feature of the present invention to provide a thin-film microelectrode array that is simple and inexpensive to fabricate.
In accordance with the present invention, an electrode is provided that is tailored for long-term, minimally invasive cortical recording or stimulation. The electrode includes a flexible element having first and second sides. The flexible element is movable between a first contracted configuration and a second expanded configuration. A contact is received in the second side of the flexible element. The contact is engagable with a cortical surface with the flexible element in the expanded configuration. A link operatively connects the contact to a control module. The link is capable of transmitting at least one of cortical recordings and cortical stimulation signals thereon.
The second side of the flexible element may be hydrophilic and the first side of the flexible element may be hydrophobic. The flexible element moves between the contracted configuration and the expanded configuration in response to a predetermined stimulus. It is contemplated for the predetermined stimulus to be voltage. A cable has a first end operatively connected to the contact and a second end connectable to the control module. A second contact may be engagable with a cortical surface with the flexible element in the expanded configuration.
In accordance with a further aspect of the present invention, a thin-film microelectrode array is provided that is tailored for long-term, minimally invasive cortical recording or stimulation. The electrode includes a flexible element that is movable between a first contracted configuration and a second expanded configuration. An array of contacts is provided on the flexible element. The contacts are engagable with a cortical surface with the flexible element in the expanded configuration. A link operatively connects the array of contacts to a control module. The link is capable of transmitting at least one of cortical recordings and cortical stimulation signals thereon.
The flexible element includes first and second sides. The second side of the flexible element may be hydrophilic and the first side of the flexible element may be hydrophobic. The flexible element moves between the contracted configuration and the expanded configuration in response to a predetermined stimulus. It is contemplated for the predetermined stimulus to be voltage. The link may include a plurality of lines. Each line has a first end operatively connected to one of the array of contacts and a second end connectable to the control module.
In accordance with a still further aspect of the present invention, a method is provided for implanting an electrode having an array of contacts on a cortical surface. The method includes the step of positioning the electrode on the cortical surface. The electrode is movable between a first contracted configuration and a second expanded configuration. Thereafter, the electrode is unfurled from the contracted configuration to the expanded configuration such that the array of contacts engages the cortical surface.
The method may include additional step of transmitting cortical recordings from the array of contacts to a control module. Alternatively, the method may include the step of transmitting cortical stimulation signals to the array of contacts. The electrode includes first and second sides. The second side of the flexible element may be hydrophilic and the first side of the flexible element may be hydrophobic. The step of unfurling the electrode may include the additional step of applying a predetermined stimulus to the electrode. It is contemplated for the predetermined stimulus to be voltage. It is also contemplated for the method to include the additional step of operatively connecting the array of contacts to a control module.